全文获取类型
收费全文 | 3329篇 |
免费 | 180篇 |
国内免费 | 1篇 |
专业分类
化学 | 2326篇 |
晶体学 | 18篇 |
力学 | 136篇 |
数学 | 548篇 |
物理学 | 482篇 |
出版年
2023年 | 7篇 |
2022年 | 14篇 |
2021年 | 24篇 |
2020年 | 37篇 |
2019年 | 43篇 |
2018年 | 62篇 |
2017年 | 38篇 |
2016年 | 132篇 |
2015年 | 97篇 |
2014年 | 107篇 |
2013年 | 230篇 |
2012年 | 249篇 |
2011年 | 268篇 |
2010年 | 140篇 |
2009年 | 155篇 |
2008年 | 214篇 |
2007年 | 221篇 |
2006年 | 211篇 |
2005年 | 216篇 |
2004年 | 180篇 |
2003年 | 161篇 |
2002年 | 118篇 |
2001年 | 30篇 |
2000年 | 24篇 |
1999年 | 35篇 |
1998年 | 12篇 |
1997年 | 14篇 |
1996年 | 24篇 |
1995年 | 20篇 |
1994年 | 9篇 |
1993年 | 20篇 |
1992年 | 15篇 |
1991年 | 15篇 |
1990年 | 13篇 |
1989年 | 14篇 |
1988年 | 6篇 |
1987年 | 14篇 |
1985年 | 24篇 |
1984年 | 27篇 |
1983年 | 8篇 |
1982年 | 26篇 |
1981年 | 13篇 |
1980年 | 26篇 |
1979年 | 28篇 |
1978年 | 18篇 |
1977年 | 20篇 |
1976年 | 26篇 |
1975年 | 19篇 |
1974年 | 18篇 |
1973年 | 16篇 |
排序方式: 共有3510条查询结果,搜索用时 0 毫秒
971.
972.
973.
974.
Guy Guerch Marcel Graffeuil Jean-François Labarre Renée Enjalbert Roger Lahana François Sournies 《Journal of Molecular Structure》1982
Structural investigation, mainly by mass spectrometry and X-ray crystallography, of the product obtained from the reaction of propylenediamine and N3P3Cl6 shows it to have a monospiro structure. It is demonstrated that in this case data collected through indirect structural methods such as IR or NMR spectroscopy could not provide a priori the right answer. 相似文献
975.
François Bry 《Journal of Combinatorial Theory, Series B》1983,34(1):48-57
Every infinite locally finite graph with exactly one 1-factor is at most 2-connected is shown. More generally a lower bound for the number of 1-factors in locally finite n-connected graphs is given. 相似文献
976.
François Bavaud 《Communications in Mathematical Physics》1990,132(3):549-554
We consider two-dimensional assemblies of particles governed by hamiltonians depending on the area and the perimeter of their convex hull. Provided the hamiltonian is quadratically homogeneous in the coordinates, we find an exact formula for the free energy. Phase transitions resulting from the competition between area and perimeter can easily be produced and explicitly dealt with. We illustrate those features by a simple example undergoing a second-order transition. 相似文献
977.
Mireille Content François Lemay Pierre Leroux 《Journal of Combinatorial Theory, Series A》1980,28(2):169-190
This paper proposes a general setting for Möbius inversion which includes the cases of locally finite partially ordered sets and monoids with the finite decomposition property (f.d.p.). The unifying concept is that of categories with the f.d.p., called Möbius categories, which we characterize in four different ways. The established theory of incidence algebras, Möbius functions, product formulas, reduced algebras, etc., is carried over. Furthermore, the study of functors between Möbius categories yields results in two directions: firstly, inspired from the substitution of formal power series is the construction of a homomorphism between incidence algebras which allows the transfer of Möbius inversions; secondly, surjective functors often give rise to a reduced incidence algebra, thus shedding new light on many important reduced algebras in combinatorial theory. 相似文献
978.
Optically active methyl-phenyl-cyclohexylphosphine sulfide is metallated by BuLi and reacted with ethyl carbonate to yield carbethoxymethyl-phenyl-cyclohexylphosphine sulfide with retention of the optical activity at phosphorus ; this sulfide is converted into the corresponding optically active functional phosphine through a nickelocene reduction-complexation. 相似文献
979.
Isopropyl 2-Phenyl 3-aziridinecarboxylate (III) obtained from isopropyl 2,3-dibromo-2,3-dihydrocinnamate (I) or isopropyl 2-bromocinnamate (II) reacts in mild conditions with hydrogen fluoride to give the isopropyl ester of 3-fluorophenylalanine (IV) in good yield. 相似文献
980.
Sonia Collin Daniel P. Vercauteren Didier Vanderveken Guy Evrard François Durant 《Journal of computer-aided molecular design》1989,3(1):39-53
Summary Molecular graphic design coupled with PCILO and crystallographic results have been used to investigate the three-dimensional structure of Tropapride, Piquindone, Zetidoline, and Metoclopramide, four dopamine D-2 receptor antagonists showing Na+-dependent binding. Three putative pharmacophoric elements, a nitrogen lone pair, a phenyl ring and a carbonyl moiety, are similarly oriented in all the Na+-dependent drugs. Conversely, for Na+-independent analogs, the two latter pharmacophoric elements play a subordinate role, but two -electron regions are systematically localized on the other side of the molecule: the first is a phenyl group while the second is a carbonyl function as in butyrophenones, a cyano group as in R48455, or a phenyl ring as in diphenylbutylpiperidines or tricyclics. The presence of a benzyl ring on this side in Tropapride might explain its weak extrapyramidal effects. 相似文献